I. Technical Field
The present invention relates to a process for producing a metal member having improved fatigue properties and corrosion resistance, and also relates to a structural member that includes a thus produced metal member, and a method of repairing a metal member.
II. Description of the Related Art
Shot peening represents a known example of a surface modification process that is used for enhancing the fatigue strength of metal materials within the structural members and the like used in aircraft and automobiles and the like (see T. Dorr and four others, “Influence of Shot Penning on Fatigue Performance of High-Strength Aluminum- and Magnesium Alloys”, The 7th International Conference on Shot Peening, 1999, Institute of Precision Mechanics, Warsaw, Poland. Internet <URL: http://www.shotpeening.org/ICSP/icsp-7-20.pdf>). Shot peening is a process in which, for example, by blasting countless particles having a particle size of approximately 0.8 mm (the shot material) together with a stream of compressed air or a compressed gas onto the surface of a metal material, indentations are formed in the surface of the metal material as a result of plastic deformation, while at the same time, the hardness of the metal material surface is increased, and a layer having compressive residual stress is formed at a certain depth.
Furthermore, shot peening treatments that employ non-metallic hard particles as the shot particles are also known. For example, ceramic particles with a particle size of not less than 150 μm, and glass-based particles comprising not less than 50% of silica SiO2 as the main constituent are widely used as shot particles.
Furthermore, in those cases where an aluminum alloy member is used as a metallic material, the material is typically subjected to an anodic oxidation treatment or the like followed by painting in order to improve the corrosion resistance and the like (see Japanese Unexamined Patent Application. Publication No. 2003-3295).
This anodic oxidation treatment is an electrolytic treatment in which, for example, an acid such as chromic acid, phosphoric acid, boric acid or sulfuric acid is used as the electrolyte and the metal material functions as the anode.